Control sequencing and prognostics health monitoring for digital power conversion and load management

Abstract

An electronics-based system (100) for power conversion and load management provides control sequencing and prognostic health monitoring and diagnostics for fault tolerant operation of the system. The system (100) includes a prognostic health monitoring and diagnostic unit (30) for identifying present out-of-range conditions, overload conditions, and trending violations, for components of the system and a decision making unit (20), which controls transitions between a plurality of operating modes to ensure fail-safe operation without unnecessary tripping, cold-starts or system resets upon the occurrence of certain fault conditions.

Description

RELATED APPLICATION[0001]This application claims priority under 35 U.S.C. §119(e) of U.S. Provisional Application 60 / 376,572 filed on Apr. 30, 2002, the entire contents of which are herein incorporated by reference.FIELD OF THE INVENTION[0002]The present invention relates to power sequencing, diagnostics and prognostics health monitoring of fault tolerant digital power conversion, distribution and load management systems. In particular, embodiments of the present invention provide modes of command / control and methods of fault tolerant operation for coordinating digital protection functions, diagnostics and health monitoring of such systems based on start-up and continuous tests, comprehensive power sequencing for achieving Soft-start, Soft-stop, ride-through and for responding to power system contingencies such as shoot-through, voltage surge, under-voltage, voltage sag, system imbalance, system under / over-frequency, over-load, critical component junction temperature and thermal man...

AI Technical Summary

Benefits of technology

[0040]By monitoring stressful periods of operation, cumulative effects of such stresses are monitored and assessed and a measure of the remaining useful life of each of the critical components is estimated in real time based upon the reliability data, present operating data and historical operating data of the critical components.

Problems solved by technology

Although electrical power conversion and distribution systems have been developed, these power conversion technologies can not presently be effectively used for mission critical “more electric” future applications (e.g., land, sea, air transport) due to the harsh operating environments and conditions resulting in very low Mean Time Between Failure (MTBF) of the main components and very limited integrated protection coordination, diagnostics and monitoring to improve overall system health and reliability.

Therefore, this system does not provide any forward-looking analysis of potential failures or real time analysis of component health.

Further, the system disclosed in U.S. Pat. No. 6,122,575 does not address component level critical devices, but only looks at the system at a subsystem level (e.g., APU).

Furthermore, such a prior art health monitoring and diagnostics system does not address low MTBF and poor reliability of power-electronics based systems because the failure modes are not mitigated thoroughly, both at the system level and component level.

Such conventional systems are not fault tolerant and due to limited Built-In-Tests (BIT) their proper operation can not be assessed at start-up or continuously monitored during normal or abnormal operation.

Furthermore, lack of proper power sequencing, Soft-start, Soft-stop, ride-through, and proper protection against contingencies such as voltage-sag, voltage surge, system imbalance, under / over-frequency, over-load, over-temperature and wrong phase sequence conditions results in very stressful situations which usually degrade or cause total failure of major components of the system.

Other limitations of prior art systems include the following:Limited operation modes—e.g., only RUN and STOP modes available.

The system is usually tripped (i.e., the load is disconnected from the power distribution system) under any abnormal condition without specifying the associated failure.

As a result, a perceived faulty unit is commonly removed from the field and sent back to the supplier.

After detailed testing and debugging in most cases, it is confirmed that the unit is capable of proper operation and consequently labeled as No Fault Found (NFF).These nuisance trips and NFFs are labor intensive, tedious and not cost effective.

User-friendly and efficient debugging of the system problems is not readily possible after a field trip / failure in a timely manner.Power sequencing (initial turn-on or turn-off of the unit) is stressful and limited operation modes do not provide a mitigation opportunity for all the known system stressful transients or failure modes.Lack of proper protection coordination, i.e., sequence, priority and timing control among different provisions of system and / or component level protection methods.Detailed system level field operation or component level limitation data is usually not available at the design time.All the failure modes or stressful periods of operation at the system or component level cannot be predicted at the time of design.Stressful periods of operation or their actual cumulative effect cannot be monitored and accounted for in real-time to estimate the remaining time-to-failure.Corrective maintenance cannot be reliably scheduled to replace degraded components to prevent components / system failure in the field during operation.A major limitation still remains in relation to overall system reliability, and the fact that conventional diagnostic systems record fault data in formats that do not aid in diagnosing future failures of the monitored components.

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